They freeze beautifully - just make sure they are carefully wrapped and you've removed all the air possible from the wrapping. I use large freezer bags, and sometimes will use a straw to draw out extra air space right before sealing the bag. As far as decorating first, I'm too chicken - afraid of colors bleeding together. Would love to hear from others about that!

I would try not to go more than two months - the shorter the time, the better. But if they're well-wrapped, without much air, they should hold up well in the freezer - I don't really know how long they can go!